Pressure-sensitive adhesive tape with primer

Abstract

A pressure-sensitive adhesive tape having a polyolefin, polyester or metal foil backing and an acrylate pressure-sensitive adhesive layer firmly adhered to the backing through a primer layer comprising a primer composition consisting essentially of an intimate mixture of a primary amino-functional trialkoxy silane and a particular carboxylated polymer component having an affinity for the acrylate adhesive. The primer composition and the silane are distributed in the primer layer in amounts of at least about five milligrams per square yard primer composition and at least about one milligram per square yard silane, and the weight ratio of silane to carboxylated polymer component is between about 1 to 10 and about 4 to 1.

What is claimed is: 
     
       1. A pressure-sensitive adhesive sheet which comprises: (1) a backing layer of (a) polyethylene or polypropylene film having one of its major surfaces activated to improve its anchorage characteristics, or (b) polyester film or (c) metal foil;   (2) a primer composition coated on one major surface of said backing layer to form a primer layer firmly adhered thereto, said major surface being for polyethylene and polypropylene films, the activated surface; and   (3) a normally tacky and pressure-sensitive acrylate adhesive layer firmly adhered to said backing layer through said primer;   wherein said primer composition consists essentially of an intimate mixture of a primary amino-functional trialkoxy silane and a carboxylated polymer component having an affinity for the acrylate adhesive layer, said carboxylated polymer component being (a) a carboxylated ethylene vinyl acetate resin, or (b) a carboxylated acrylic adhesive polymer, or (c) the combination of a major amount of a polyester polymer and a minor amount of a carboxylated acrylic adhesive polymer; and   wherein said primer composition is distributed in the primer layer in such amounts as to provide at least about five milligrams per square yard of primer composition and at least about one milligram per square yard of silane, with the weight ratio of silane to carboxylated polymer component being between about 1 to 10 and about 4 to 1.   
     
     
       2. A pressure-sensitive adhesive sheet according to claim 1, wherein the carboxylated ethylene vinyl acetate resin is the terpolymer of ethylene, vinyl acetate and acrylic or methacrylic acid. 
     
     
       3. A pressure-sensitive adhesive sheet according to claim 2, wherein the vinyl acetate content of the ethylene vinyl acetate resin is between about 20 and 30 weight percent. 
     
     
       4. A pressure-sensitive adhesive sheet according to claim 1, wherein the carboxylated acrylic adhesive polymer comprises a major amount of medium chain length aklyl acrylate monomer component and a minor amount of cohesion inducing short chain monomer component. 
     
     
       5. A pressure-sensitive adhesive sheet according to claim 4, wherein the carboxylated acrylic adhesive polymer includes an acrylic or methacrylic acid component. 
     
     
       6. A pressure-sensitive adhesive sheet according to claim 1, wherein the polyester polymer is a lower melting point mixed polyester. 
     
     
       7. A pressure-sensitive adhesive sheet according to claim 6, wherein the mixed polyester is polymerized from propylene glycol, glycerol, terephthalic acid and isophthalic acid. 
     
     
       8. A pressure-sensitive adhesive sheet according to claim 1, wherein the silane is N(beta-aminoethyl) gamma-aminopropyltrimethoxysilane. 
     
     
       9. A pressure-sensitive adhesive sheet according to claim 1, wherein said acrylate adhesive layer is coated over said primer in the form of an adhesive composition comprising a copolymer of monomers comprising (a) a major amount of a medium chain length alkyl acrylate monomer averaging about 4-12 carbon atoms in the alcohol moiety, and said major amount being from about 60 to 80 parts by weight of total adhesive monomer solids, and   (b) a minor amount of a cohesion inducing short chain monomer copolymerizable with the other monomers, said minor amount being from about 10 to 30 parts by weight based on total weight of adhesive solids.   
     
     
       10. A pressure-sensitive adhesive sheet according to claim 9, wherein said adhesive monomers also include an alkoxy silyl cross-linking monomer having an unsaturated functional terminal group copolymerizable with the other monomers. 
     
     
       11. A pressure-sensitive adhesive sheet according to claim 9, wherein said adhesive monomers also include an unsaturated carboxylic acid monomer copolymerizable with the other monomers.